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Agriculture In A Post-Oil Economy

By Peter Goodchild

22 September, 2007

The decline in the world’s oil supply offers no sudden dramatic event that would appeal to the writer of "apocalyptic" science fiction: no mushroom clouds, no flying saucers, no giant meteorites. The future will be just like today, only tougher. Oil depletion is basically just a matter of overpopulation — too many people and not enough resources. The most serious consequence will be a lack of food. The problem of oil therefore leads, in an apparently mundane fashion, to the problem of farming.

To what extent could food be produced in a world without fossil fuels? In the year 2000, humanity consumed about 30 billion barrels of oil, but the supply is starting to run out; without oil and natural gas, there will be no fuel, no asphalt, no plastics, no chemical fertilizer. Most people in modern industrial civilization live on food that was bought from a local supermarket, but such food will not always be available. Agriculture in the future will be largely a "family affair": without motorized vehicles, food will have to be produced not far from where it was consumed. But what crops should be grown? How much land would be needed? Where could people be supported by such methods of agriculture?


The most practical diet would be largely vegetarian, for several reasons. In the first place, vegetable production requires far less land than animal production. Even the pasture land for a cow is about one hectare, and more land is needed to produce hay, grain, and other foods for that animal. One could supply the same amount of useable protein from vegetable sources on a fraction of a hectare, as Frances Moore Lappé pointed out in 1971 in Diet for a Small Planet [12]. Secondly, vegetable production is less complicated. The raising of animals is not easy, and one of the principles to work with is, "The more parts there are to a machine, the more things there are that can go wrong." The third problem is that of cost: animals get sick, animals need to be fed, animals need to be enclosed, and the bills add up quickly. Finally, vegetable food requires less labor than animal food to produce; less labor, in turn, means more time to spend on other things. A largely vegetarian diet is also the most healthful, but that is a separate issue.

With a largely vegetarian diet, one must beware of deficiencies in vitamins A and B12, iron, calcium, and fat, all of which can be found in animal food. Most of these deficiencies are covered by an occasional taste of meat; daily portions of beef and pork are really not necessary. Animal food should be used whenever it is available, but it is not a daily necessity.

Of vegetable foods, it is grains in particular that are essential to human diet. Thousands of years ago, our ancestors took various species of grass and converted them into the plants on which human life now depends. Wheat, rice, maize, barley, rye, oats, sorghum, millet — these are the grasses people eat every day, and it is these or other grasses that are fed (too often) to the pigs and cows that are killed as other food. A diet of green vegetables would be slow starvation; it is bread and rice that supply the thousands of kilocalories that keep us alive from day to day.

In general, the types of crops to grow would be those which are trouble-free, provide a large amount of carbohydrates per unit of land, provide protein, and supply adequate amounts of vitamins and minerals. Most grains meet several of these requirements. Winter (not summer) squashes are also high in kilocalories. Parsnips rate high in kilocalories, whereas carrots, turnips, rutabagas, and beets are slightly lower on the scale. Beans (as "dry beans") rate fairly well in terms of kilocalories, and they are the best vegetable source of protein, especially if they are eaten with maize or other grains with complementary amino acids.


The amount of land needed for farming with manual labor would depend on several factors: the type of soil, the climate, the kinds of crops to be grown. The highest-yielding varieties are not necessarily the most disease-resistant, or the most suitable for the climate or the soil, or the easiest to store. The weather also makes a big difference: too little rain can damage a crop, and too much rain can do the same. Unusually cold weather can damage some crops, and unusually hot weather can damage others. Without irrigation — relying solely on rain — the yield is less than if the crops were watered.

But here are some rough figures. Let us use the production of maize (corn) as the basis for our calculations, and for now let us pretend that someone is going to live entirely on maize. "Maize" or "corn" here does not mean the vegetable that is normally eaten as "corn on the cob," but the types that are mainly used to produce cornmeal; these are sometimes referred to as "grain corn" or "field corn." Maize is very high-yielding and can be grown easily with hand tools, but it is only practical in areas with long periods of warmth and sunshine; even in most parts of North America it is not easy to grow north of about latitude 45.

A hard-working adult burns about 5,000 kcal per day, or 1.8 million kcal per year. David Pimentel [14] mentions a study of slash-and-burn maize culture in Mexico that produced 1,944 kg of maize per hectare, or 6.9 million kcal. Under such conditions, then, a hectare of maize would support approximately 4 people.

Potatoes require about 50% less land than "grain-corn" maize, but they are troublesome in terms of insects and diseases. Wheat, on the other hand, requires approximately 50% more land than maize to produce the same amount of kilocalories. Beans require about 100% more land than maize. "Root crops" such as turnips, carrots, or beets have yields at least 10 times greater than maize, but they also have a much higher water content; their actual yield in kilocalories per hectare is slightly less than that of maize.

To determine whether a country can feed itself with manual labor, we need to look at the ratio of population to arable land. With manual labor, as noted, a hectare of maize-producing land can support only 4 people. Any country with a larger ratio than that would be undergoing famine. The problem might be relieved to some extent by international aid, but without fossil fuels for transportation such international aid would be negligible. And this ratio is for maize, a high-yield crop; we are also assuming that crops will not be wasted by feeding them to livestock in large amounts.

In the present year of 2007, the world as a whole has a population-to-arable ratio of slightly over 3:1. Conversely, less than a third of the world’s 200-odd countries actually pass that test, and many of those are countries that have relatively low population density only because they have been ravaged by war or other forms of political turmoil. The Arabian Peninsula, most of eastern Asia, and most of the Pacific islands are far too crowded. Even the UK scores badly at 11:1. If we meld UN figures [17] with those of Gordon and Suzuki [9] and assume that the world population in 2030 will be about 11 billion, then even fewer countries will be within that 4:1 ratio. There might be serious conflicts between the haves and the have-nots, and isolationism might be a common response.


Most of the world’s land is not suitable for agriculture. Either the soil is not fertile or the climate is too severe. In most areas, if the soil is really poor to begin with there is not much that can be done about it, at least with the resources available in a survival situation.

Soil science is a complicated subject. Roughly speaking, however, good soil contains both rock material and plant material (humus). The rock material includes 16 elements of importance: boron, calcium, carbon, chlorine, copper, hydrogen, iron, magnesium, manganese, molybdenum, nitrogen, oxygen, phosphorus, potassium, sulfur, and zinc. (Actually the C, H, and O are mainly from air or water.) The plant material (humus) acts in 3 ways: (1) mechanically — it holds air and water; (2) chemically — it contains a large amount of C, H, and O, and a little (frequently too little) of the other 13 elements; and (3) biologically — it contains useful organisms.

Of the 16 elements, the most critical are phosphorus (P), potassium (K), and especially nitrogen (N); calcium and magnesium are probably next in importance. These elements might be abundant in the virgin soil before any cultivation is done, but wherever crops are harvested a certain amount of the 3 critical elements is being removed. The usual solution is to add fertilizer, which can be artificial or can come from such sources as rock dust.

As Donald P. Hopkins [10] explained in 1948, (a) organic matter is not an ideal substitute for (b) fertilizer (i.e. the 16 elements), nor is (b) fertilizer an ideal substitute for (a) organic matter. A few centuries ago, animal manure was high in N-P-K etc., but that is rarely the case today unless the manure itself originates in feed that was artificially fertilized. Nevertheless, in a survival situation, organic matter may be the only available source of the essential elements.

Native people in many countries had a simple solution to the problem of maintaining fertility: abandonment. No fertilizer was used, except for the ashes from burned undergrowth and from burned crop residues. As a result, of course, the soil became exhausted after a few years, so the fields were abandoned and new ones were dug. Sometimes such a technique is called "slash-and-burn." On a large scale the technique would mean leaving behind a long string of what used to be called "worked-out farms." For a large population, such a method would be impractical, in fact catastrophic. On a very small scale, however, it might be all that is possible; in any case, the abandoned spot would, over many years, revert to reasonably fertile land, at least in terms of humus content, and there might be wild legumes to replace the nitrogen.

Actually, if abandoned land is taken up again at a later date, the practice of abandonment tends to overlap with that of fallowing, another practice to be found in many societies. With the traditional European method of fallowing, part the land is left to revert to grass and weeds for perhaps a year before being plowed again.

A common partial solution to the N-P-K problem has been to turn crop waste into compost and put it back onto the land. The problem with that technique, however, is that one cannot create a perpetual-motion machine: every time the compost is recycled, a certain amount of N-P-K is lost, mainly in the form of human or farm-animal excrement, but also as direct leaching and evaporation. One could recycle those wastes, but the recycling will always have a diminishing return. Of the 3 most important elements, nitrogen is by far the most subject to loss by leaching, but to some extent that can also happen with phosphorus and potassium.

In the original "organic gardening" movement pioneered by Sir Albert Howard in the early years of the 20th century, nothing but vegetable compost and animal manure was allowed. In modern organic gardening, on the other hand, a common technique is to replace lost elements by adding powdered rock, particularly rock phosphate and granite dust. For "non-organic" gardeners and farmers, the usual response to the problem of soil replenishment is to apply artificial fertilizer, N-P-K largely derived from those same types of rock used in organic gardening. (In fact, the use of rock powders in present-day organic gardening sounds suspiciously like a drift toward artificial fertilizers.) If the fragile international networks of civilization break down, however, then neither rock powders nor artificial fertilizer will be readily available. They are very much the products of civilization, requiring a market system that ties together an entire country, or an entire world.

Writing early in the 20th century, F.H. King [11] claimed that farmers in China, Japan, and Korea were managing to grow abundant crops on about 1/10 of the cultivable land per capita as Americans, and that they had done so for 4,000 years. What was their secret? The answer, in part, is that most of eastern Asia has an excellent climate, with rainfall most abundant when it is most needed. More importantly, agriculture was sustained by the practice of returning almost all waste to the soil — even human excrement from the cities was carried long distances to the farms. Various legumes, grown in the fields between the planting of food crops, fixed atmospheric nitrogen in the soil. Much of the annually depleted N-P-K, however, was replaced by taking vegetation from the hillsides and mountains, and by the use of silt, which was taken from the irrigation canals but which originated in the mountains. The Asian system, therefore, was not a closed system, because it took materials from outside the farms, and these materials came from areas of naturally high fertility.


One way of determining when oil-based agriculture will be abandoned is strictly economic: when it costs farmers more money to use machinery than to use hand tools, they will go back to hand tools. In the study of Mexican labor mentioned by Pimentel, "a total of 1,144 hours of labor was required to raise a hectare of corn." Pimentel then compares that labor with the mechanized corn production in the United States, telling us that "600 liters of oil equivalents [for fuel, fertilizer, and pesticides] are required to cultivate 1 ha of corn." The ratio of hours to liters therefore seems to be approximately 2:1.

Modern grain-corn production in the US, however, results in yields of about 6,000 kg/ha, about 3 times as great as in the Mexican example. If we include that factor of higher yield, the previous 2:1 ratio of hours/liters must really be regarded as 6:1.

To discover whether mechanization is cost-effective, we must insert a number for hourly wage. If the laborer is self-employed, however, the figure for hourly wage seems purely imaginary: If costs are rising, for example, can the laborers not simply pay themselves less? Only to a certain degree. The laborer’s wage is often as little as it takes to keep body and soul together, but anything less than that subsistence wage would make farming impossible.

The rise in the price of fuel, combined with the hourly wage, then, determines the cut-off point for mechanized labor. When farmers pay themselves a certain amount for 6 hours of work, but the price of fuel is equal to that amount, the 6:1 ratio has been reached, and it would be reasonable for the farmer to give up mechanization.

Two other factors must be included if we are to compare manual labor with mechanization. Capital costs are higher with mechanization: a tractor must be paid for, there are repairs to consider, and eventually the tractor must be replaced. For now, however, let us assume that the laborer is working with a minimum of equipment. Secondly, in spite of what was said above about subsistence wages, farming income is higher in some countries than in others, and the same can be said of fuel costs. Farmers in Mexico, with high fuel costs and low wages, might be inclined to abandon mechanization sooner than farmers in the United States.

Food, of course, can also be produced with the labor of horses or oxen, and in fact many hours of human labor can thereby by saved. Even if animals are fed only on forage, however, a good deal of land is needed for that purpose. It is also questionable whether large numbers of horses or oxen could be bred and distributed in the next few decades. There is also the question of "alternative energy," in the sense of solutions involving advanced technology, but such innovations would probably serve little purpose without fossil fuels to provided at least an infrastructure [7,8].

What will be the price of gasoline in a few years’ time? ("Current dollars" are used here; it is misleading to speak of "inflation-adjusted energy prices," since it is mainly energy shortages that cause inflation in the first place [3].) US gasoline prices increased over the quarter-century before 2003 only at the same rate as the median income [16], with the exception of some small deviations during periods of warfare. In recent years, however, prices have risen by 18% per year [6]. With such a growth trend, a gallon of US gasoline will cost $60 in 2025, and $140 in 2030, although number-juggling of that sort soon becomes highly speculative.

For the sake of a thought-experiment, however, we might take a closer look at those price projections. Let us recall the 6:1 ratio of hours-versus-liters at which it is no longer cost-effective to use mechanization. A cost of $140/gallon in 2030 would equal $36/liter. If 6 hours of labor should also happen to cost $36, a sensible farmer would decide to give up mechanization at that point. In countries poorer than the US, that cut-off point would actually arrive well before the year 2030.

The other way of estimating a cut-off date for oil-based agriculture, of course, is to look at predictions of the decline in global oil production. According to the latest annual report of BP Global [1], "proved reserves" are only 1.2 trillion barrels (excluding a little from Canadian tar sands), although that figure inches up slightly from one annual report to another. A trillion barrels of oil is not enough to stretch more than a few decades. A continuation of an 18% annual increase in the cost of gasoline may seem absurd, but that figure closely matches the likely bell curve for global oil production: a decline from 30 billion barrels (5 barrels per person) in the year 2000 to 11 billion barrels (1 barrel per person) in 2030 would be an average annual decrease of 22%. It is not only gasoline prices and estimated oil reserves that have an ominous chronological relationship: it is surely not merely coincidental that there has recently been a spate of legislation, in several countries, for ethanol and other biofuels, in spite of the economic and ecological absurdity of such forms of "alternative energy."


1. BP Global Statistical Review of World Energy. Annual.

2. Bradley, Fern Marshall, and Barbara W. Ellis, eds. Rodale’s All-New Encyclopedia of Organic Gardening. Emmaus, Pennyslvania: Rodale, 1992.

3. Chin, Larry. "Peak Oil and the Inflation Lie." Global Research, May 19, 2007.

4. CIA World Factbook.

5. Davis, Adelle. Let’s Eat Right to Keep Fit. Rev. ed. New York: Harcourt Brace Jovanovich, 1970.

6. Energy Information Administration, US Department of Energy. "Retail Motor Gasoline and On-Highway Diesel Fuel Prices, 1949-2006."

7. Goodchild, Peter. "Peak Oil and the Myth of Alternative Energy." Countercurrents. Sept. 6, 2006.

8. -----. "Peak Oil and the Problem of Infrastructure." Countercurrents. Sept. 29, 2006.

9. Gordon, Anita, and David Suzuki. It’s a Matter of Survival. Toronto: Stoddart, 1990.

10. Hopkins, Donald P. Chemicals, Humus, and the Soil. Brooklyn, NY: Chemical Publishing, 1948.

11. King, F.H. Farmers of Forty Centuries. Emmaus, Pennsylvania: Organic Gardening, n.d.

12. Lappé, Frances Moore. Diet for a Small Planet. New York: Ballantine, 1971.

13. Logsdon, Gene. Small-Scale Grain Raising. Emmaus, Pennyslvania: Rodale, 1977.

14. Pimentel, David, and Carl W. Hall, eds. Food and Energy Resources. Orlando, Florida: Academic P, 1984.

15. Thompson, Paul. "Which Countries Will Survive Best?"

16. United States Census Bureau. "Historical Income Tables — Families." US Government Printing Office, annual.

17. United Nations Population Fund. The State of the World Population. Annual. New York: United Nations.

Peter Goodchild is the author of Survival Skills of the North American Indians (Chicago Review P, 2nd ed., 1999). He can be reached at [email protected].

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